N-Hydroxy-2-acetylaminoflorene (NOH-2AAF) is converted by sulfotransferase enzymes present in rat liver 100,000 x g supernatant to an electrophilic N-O-sulfate ester which covalently binds to protein and DNA. Ascorbic acid inhibits the covalent binding of the electrophilic species to both protein and DNA, but increases the observed mutagenesis by ten-fold. These data show an inverse relationship between DNA and protein covalent binding and mutagenesis of N-hydroxy-acetylarylamides.